This invention relates to curved escalators and more particularly to frame structures for a curved escalators having a circular stairway path that has a circular horizontal projection.
Curved escalators include a frame structure defining therein a stairway path along which a plurality of segment steps travel. The stairway path includes upper and lower horizontal landing sections and an intermediate inclined section connected between the upper and lower landing sections.
As illustrated in FIGS. 1 and 2, a curved escalator 1 has a stairway path 2 of a spiral or circular in horiziontal projection along which a plurality of segment steps 3 travel. The steps 3 are connected to an endless belt 5 mounted within a frame structure 4 and are driven by a drive unit 6. Endless moving handrails 7 are also disposed for synchronized movement with the steps 3 on the endless belt 5. One of the proposed structures for the main frame structure 4 of a curved escalator utilizes a plurality of truss units, each of which is comprised of upper and lower cord members and vertical members, connected to each other to define a curved or circular frame structure 40 as shown in FIG. 3, in which the frame structure 40 is illustrated in a plan view. As shown in the figure, the frame structure 40 comprises truss units 40a, 40b, 40c . . . 40n which are connected to each other and arranged along a curve formed by smoothly connected arcs having radii of curvature R.sub.1 to R.sub.5 with respect to the centers O.sub.1 to O.sub.5 to form a polygonal truss structure. The frame structure 40 has upper and lower horizontal sections along which the upper and lower landing sections of the stairway path are defined, and an intermediate, inclined section along which the sloped section of the stairway path is defined.
However, according to the prior design described above, the upper and lower horizontal sections of the frame structure and the inclined section of the frame structure are directly connected with a single angled point therebetween. That is, the horizontal section of the frame structure abruptly changes into the inclined section, and the cord (as used herein, "cord" and/or "cordal" refer to certain non-vertical structural members as well as a straight line joining two points on an arc) member of the horizontal section must be angled at a relatively large angle to change into the cord member of the inclined section. The cord members have mounted thereon vertical members which carry cross members extending between outer and inner side members, and guide rails for guiding the steps of the escalator are mounted to the cross members to extend along the stairway path of the escalator.
With the above arrangement, since the cord members are connected at the bent point or the connecting point between the horizontal section and the sloped section, the vertical distance between the top face of the truss and the tread of the guide rail is not constant at the position at which the vertical member is mounted, requiring much time and money to accurately position the guide rails.
Further, since the truss members have varying cross sections, mounting brackets to be supported from the truss members must be formed accordingly, resulting in an increased number of parts and cost.
Also, since the positioning of the vertical member is very complicated, the assembly of the vertical member that is vertically disposed between the upper and the lower cord members is complicated and difficult. The positioning of the truss members is also difficult. Further, the positioning of the guide rails in the radial direction within truss units arranged along a curve is difficult because the truss units themselves are constructed of straight truss members.